When casting round balls for m/l use, the balls should be as soft as possible. I don't flux round ball lead because fluxing causes any unwanted tin , and other alloys that harden ball lead to mix w/the good stuff. Tin , antimony , etc float to the top in the pot and should be skimmed off with the dirt. Fluxing came into use when folks began to make bullets for modern ctg. rounds where velocity is higher . So ,don't flux , skim the crap off the top before you pour metal for r/b's.